Should you trust HRV values your wearable gives you?

Should you trust HRV values your wearable gives you?

My experience as an athlete

As a health coach and fitness trainer and being 53 I place a huge importance on the optimization of my health. I also love to challenge what I call conventional stupidity approach to health, fitness and life. I do things a bit differently than most Triathletes and Marathoners and Personal Trainers. I fundamentally believe we need to rest more, reduce chronic stress, and connect more with what is going on in our bodies.

I use a wide range of subjective measures in relation to my health and fitness. Subjective measures such as how I feel, my energy levels, my bowel movements, my mood, my ability to think and make decisions, and of course how I feel when I am in the gym, the pool, the track or on the bike. Some people place a lot of importance on Objective metrics and numbers and tend to negate the Subjective measures.

I think it is very important to have a good balance between both.

I recently found this to be important when I started looking at biometrics. I was looking at my RHR, O2 Saturation, Respiration and HRV all from a nocturnal measurement lens. I found there was a trend for my HRV to be quite low and I mean low 32, 41, 35, and it did not vary much regardless of if I had had a 5 hr training day or a rest day. It also did not vary based on my RHR, or how I felt. I was very confused. I was worried, I was starting to think something was wrong. There was a huge disconnect between the subjective rating I would give myself for my state and the objective numbers provided by the HRV tool I was using.

So I tried several HRV devices/applications and tools and they all seemed to show the same result. I was desperate for a deeper understanding of what was going on.

My experience with Biostrap

So why is this so important? Well I am a serious AG athlete. Last year I raced in the 70.3 Ironman World Championships and I train about 13 hrs a week and I am serious about my sport. This was important to me. I also feel that recovery is one of the key pillars of health and fitness.

The last thing I want to do is cause further stress to my body that would impact my ability to recover, ie doing a solid training session when not fully recovered.

I started looking at a system for biometrics that to me appeared to be more focussed on HRV than simple fitness tracking, it also provided the ability to do a 2 minute biometric scan. I decided to give this a trial. It is called a biostrap.

I had been hearing a lot about the fact that nocturnal HRV reading for elite athletes could be not effective due to a phenomenon called “parasympathetic saturation”

My understanding is that this has been reported in high level ultra-marathoners, triathletes and endurance athletes that are more susceptible to it in the supine position simply because you’re in a more rested or relaxed state where our heart is not being challenged to overcome gravity, to pump blood upwards and so forth. When you already have a very low RHR lying down makes it even worse.

Andrew Flatt PhD, CSCS

“Parasympathetic saturation, the results of would be having decreased heart rate variability despite having a very low resting heart rate, which is counterintuitive because typically, the lower your resting heart rate, the higher your heart rate variability is. There tends to be an inverse relationship there. But what’s happening kind of physiologically is that the acetylcholine receptors on the heart that respond to vagal stimulation, the vagus nerve is going to release acetylcholine which will bind to the muscarinic cholinergic receptors on the heart, and that tends to slow heart rate down”

So after reading all of this one morning before training I decided to conduct a Sitting biometric scan.

“Kiviniemi et al. (2007) provides a very thorough explanation of why HRV might be better measured in a standing position as opposed to seated or supine. Essentially, HRV is susceptible to saturation of the parasympathetic nervous system in subjects with low heart rates”

Yes, this is me at 36-41 RHR. I got excited maybe I found the reason why my Nocturnal HRV was so low. He further explains:

"Mourout et al (2004) saw decreased HRV in overtrained athletes compared to not overtrained athletes in the supine position. Similar results were found when HRV was measured after 60 degree tilt. The non-OT group always had higher HRV in the standing position and saw greater reactivity to the postural change. Therefore, pick a position and stick to it 100% of the time for your values to be meaningful. Switching positions from day to day will provide skewed data."

Endurance athletes and athletes with low resting heart rates (yes that’s me) are probably better off measuring HRV in a standing position. We understand that when an elite athlete has a very low RHR then they are likely to bein a state of parasympathetic saturation. Andrew Flatt Explains this as follows:

“This is when vagal HRV markers (e.g., lnRMSSD) are low despite a low resting heart rate. This has to do with excess acetylcholine within the myocardium that maintains inhibitory actions on the SA node, and thus limits the typical arrhythmia observed from respiration. See below”

“There are several potential explanations for the decrease in HRV with increasing parasympathetic effect. If with increasing blood pressure there is higher-frequency vagal discharge and inspiratory suppression is maintained,18 23 then there must be persistent parasympathetic effect during inspiration despite the suppression of vagal nerve discharge. In in vitro preparations, the dose-response curve to acetylcholine has a rapidly rising portion and at higher concentrations is flat,24 25 displaying a simple saturation relationship. High-intensity vagal nerve discharges during expiration may release enough acetylcholine to result in saturation of the parasympathetic effect during expiration. If acetylcholine concentrations during expiration are high enough, the expected decline in acetylcholine concentrations in the region of the sinus node during inspiration may not be enough to significantly diminish the parasympathetic effect. Alternatively, it is possible that with increasing blood pressure, there is loss of phasic respiratory changes in vagal nerve discharges,26 resulting in a loss of phasic effect and a decrease in HRV. It is unclear which mechanism is operative in humans.”

So if you are using an HRV device, and you have a low RHR maybe you should do a self check and consider are your Objective numbers from your HRV app lining up with the Subjective measures and, if not, consider using a device that allows you to do a sitting or standing biometric scan.

Andre Obradovic

Andre Obradovic is a ICF certified PCC level coach. He works with motivated individuals and executives to help them regain control of their life and achieve optimum performance. Andre is a USA Triathlon Level I Certified Coach, Triathlon Australia Development Coach, Certified Health Coach & Personal Trainer. He is a passionate triathlete and marathoner in the 50-54 age group.